1. Field of the Invention
The present invention relates to a window-raising device for a motor vehicle, comprising rotary drive means, a transmission belt which follows a closed path passing onto a drum connected to the drive means and onto upper and lower return pads having curved convex tracks onto which the belt passes by sliding, a carriage affixed to the window and to the flexible transmission element between the upper and lower return pads, and guidance means connected to this carriage, the belt being provided with engagement means which cooperate with corresponding engagement means provided on the drum.
2. Discussion of the Background and Relevant Information
With respect to conventional devices having a cable and pulleys, the window-raising devices of this type have the advantage of a lesser weight, good resistance to water and especially an excellent durability even in the absence of maintenance work, while having a competitive price by virtue of the use of a majority of parts made of synthetic molded material EP-A-0 023 474 describes such a device, in which the motor mechanism comprises a planet gear adapted to either allow alternatively a motorized drive or a manual drive by handle. In effect, one knows that in this case any breakdown hindering the operation of the motor has the effect of hindering all movement of the window, even by a manual drive of the main shaft of the mechanism, because the latter is blocked by the reducer connected to the motor. The solution adopted in the known device consists of connecting the reducer to the main shaft by means of a planet gear whose satellite plate is connected to a reserve manual drive. However, this solution is disadvantageous because such a mechanism is relatively costly, cumbersome and heavy. In addition, one must block the rotation of the satellite plate to allow the motorized drive and likewise prevent the mechanism from being able to turn under the effect of a diminishing pressure applied to the window by a burglar trying to force the door.